A blood pressure is one index for analyzing the presence or absence of a cardiovascular disease. For example, analysis based on a blood pressure of a risk such as a so-called lifestyle-related disease is effective for preventing diseases in the cardiovascular system such as stroke, heart failure, and heart attack. Specifically, at outside of the hospital such as at home, it is desirable to measure a blood pressure over a long period at the same time every day in a fixed (or substantially fixed) environment. A blood pressure measured outside of the hospital is suitable for predicting diseases in the cardiovascular system with a high degree of accuracy. Therefore, a blood pressure measured outside of the hospital such as at home tends to be emphasized in medical practice. Further, it is also very important for curing hypertension to accurately measure a blood pressure.
A blood pressure fluctuates depending on a living activity pattern in a time period such as one year, one month, or 24 hours. Further, the blood pressure greatly fluctuates depending on various factors such as an activity amount, conversation, psychological anxiety, tension, impatience, astonishment, patience, alcohol-intake, smoking, and coldness other than pathological factors.
Research has also been conducted in recent years for estimating a risk of occurrence of a disorder in an organ on the basis of a difference among a blood pressure measured while sleeping, a blood pressure measured while being active, and a blood pressure measured when waking up in the morning.
For example, a blood pressure meter (ABPM) disclosed by PTL 1 and PTL 2 is a blood pressure meter that regularly measures a blood pressure by being carried by a person to be measured for 24 hours in order to measure a blood pressure in various situations. ABPM is an abbreviation for Ambulatory_Blood_Pressure_Monitoring. According to “Guidelines for Usage (ABPM) Standards of Blood Pressure Meters Carried for 24 Hours,” a measurement interval is a time interval ranging from 10 to 30 minutes. Further, according to the guidelines, it is necessary for a person to be measured to record daily activities (e.g. bedtime, wake-up time, sleep depth, meals, excretions, dosing, and the like).
PTL 3 to PTL 5 disclose common blood pressure meters (blood pressure measurement devices).
PTL 3 discloses a Non Invasive blood pressure measurement device in which the noise can be eliminated and which has a small burden on a person to be measured. The blood pressure measurement device includes a function for eliminating noise from a measured pulse wave.
The blood pressure measurement device disclosed in PTL 4 measures pulse waves with a plurality of pulse wave sensors and calculates a starting time of a pulse wave having a largest amplitude of the measured pulse waves. The blood pressure measurement device calculates an internal pressure of a cuff at the calculated point of time as a maximum blood pressure.
The electronic blood pressure meter disclosed in PTL 5 includes an oscillometric measurement unit for measuring a blood pressure on the basis of a pulse wave and a calculation unit for calculating a waveform parameter representing a waveform corresponding to a relative pressure of the pulse wave to an internal pressure of a cuff. The electronic blood pressure meter further includes an update unit for calibrating the calculated blood pressure on the basis of the calculated waveform parameter.